Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geological formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production of oil and gas can begin.
Well pipe such as coiled or threaded production tubing, for example, is surrounded by an annular space between the exterior wall of the tubing and the interior wall of the casing or borehole wall. Frequently, it is necessary to seal this annular space between upper and lower portions of the well depth. It is often desired to utilize packers to form an annular seal in wellbores. Open-hole packers provide an annular seal between the earthen sidewall of the wellbore and a tubular. Cased-hole packers provide an annular seal between an outer tubular and an inner tubular. The sealing element of a packer is a ring of rubber or other elastomer that is secured and sealed to the interior wall surface which may be the interior casing wall or the borehole wall. By compression, for example, the ring of rubber is expanded radially against the casing or borehole wall.
Common types of packers include inflatable packers, mechanical expandable packers, and swell packers. Inflatable packers typically carry a bladder that may be pressurized to expand outwardly to form the annular seal. Mechanical expandable packers have a flexible material expanding against the outer casing or wall of the formation when compressed in the axial direction of the well. Swell packers comprise a sealing material that increases in volume and expands radially outward when a particular fluid contacts and diffuses into the sealing material in the well. For example the sealing material may swell in response to exposure to a hydrocarbon fluid or to exposure to water in the well. The sealing material may be constructed of a rubber compound or other suitable swellable material.
The benefits of using swellable seal materials in well packers are well known. For example, typical swellable seal materials can conform to irregular well surfaces and can expand radially outward without the use of complex and potentially failure-prone downhole mechanisms. Swell packers are isolation tools that utilize elastomer swelling to provide a barrier in casing/open hole and casing/tubing annuli. These packers may have a water reactive section, an oil reactive section or both. A water reactive section may consist of water-absorbing particles incorporated into a polymer. These particles swell by absorbing water, which in turn expands the rubber. An oil reactive section may utilize oleophilic polymers that absorbs hydrocarbons into the matrix. This process may be a physical uptake of the hydrocarbons which swells, lubricates and decreases the mechanical strength of the material as it expands, limiting the maximum differential pressure that can be applied across the packer. Moreover, the material deswells in the absence of a triggering fluid resulting in a loss of the annular seal upon changes to the wellbore fluid environment.
It would be an advance in the art if the elastomers used in swellable seals could be improved that when swollen are mechanically stronger and more durable. Further, it would be an advance in the art if the elastomer did not deswell in the absence of the triggering fluid.
The presently disclosed subject matter addresses the problems of the prior art by reinforcing the elastomeric composition. The presently disclosed subject matter discloses elastomer compositions that swell and stiffen but do not substantially degrade or disintegrate upon long term exposure to particular fluids.